Electrically controlled brake system

ABSTRACT

An electrically controlled brake system  10  for a tractor is provided that is equipped with an anti-jackknifing brake that can be actuated by means of a manual operating element and that acts only on the brakes of a trailer coupled to the tractor. The operating element is an electrical element which generates an electrical signal to control a valve device by means of which the braking force of the anti-jackknifing brake can be increased.

BACKGROUND OF THE INVENTION

The present invention is directed generally to a new electricallycontrolled brake system for a tractor, the system including a manuallyactuatable anti-jackknifing brake that acts only on the brakes of atrailer connected to the tractor.

Brake systems with anti-jackknifing brakes are known. Anti-jackknifingbrakes are used, for example, to maintain appropriate spacing ondownhill grades between the tractor and the trailer in a vehicle train.Such anti-jackknifing brakes are also used advantageously on leveldriving surfaces. Further, anti-jackknifing brakes are useful fortesting the braking effect of the trailer. Further still, the connectionof the tractor to the trailer can also be tested with anti-jackknifingbrakes.

In conventional brake systems with anti-jackknifing brakes, the servicebrake of the trailer is actuated via a manual lever in the vehicleoperator's cab in order to brake only the trailer (the tractor is notbraked during manual actuation of the lever). Such conventionalanti-jackknifing brakes are, however, pneumatically actuated. For thispurpose, the manual lever in the operator's cab is in pneumaticcommunication with the brake system. This is a disadvantage sincecompressed-air lines must be installed in the operator's cab, whichtherefore makes the brake system more expensive. Also, more stringentsafety requirements must be satisfied when compressed-air lines arerouted in an operator's cab, also contributing to the greater cost.Furthermore, the routing of compressed-air lines in an operator's cabimposes a considerable demand for space in the cab, at the expense ofthe operator's comfort.

It is, accordingly, desired to provide an improved brake system with ananti-jackknifing brake function.

SUMMARY OF THE INVENTION

Generally speaking, in accordance with the present invention, a brakesystem with an anti-jackknifing brake function is provided wherein theoperating element is a manually operable electrical operating elementwhich generates an electrical signal to control a valve device whichinfluences the braking force of the anti-jackknifing brake.

By the use of an electrical operating element to control theanti-jackknifing brake, the installation of compressed-air lines in theoperator's cab can be avoided. It is necessary only to route electricallines, which are substantially more flexible, more space-saving and lessexpensive. The electrical operating element can be disposed in theoperator's cab such that it can be manually operated without difficultyby the operator, and be independent of the foot brake pedal by means ofwhich the service brake of the vehicle is actuated.

The electrical operating element generates an electrical signal, which,either directly or after pre-processing in a suitable control device,operates a valve device by means of which the braking force of theanti-jackknifing brake can be increased (i.e., the braking force on thewheels of the trailer can be increased).

The electrical signal generated by the electrical operating element canbe an analog signal or a digital signal that can be varied infinitely orin multiple stages to represent a plurality of different values. In thisway, the braking force exerted by the anti-jackknifing brake can beapplied in infinite variations or multiple stages.

Advantageously, the braking force of the anti-jackknifing brake isgenerated by means of a spring-actuated brake cylinder of the trailer.Spring-actuated brake cylinders are commonly used in trailers. Thus, usecan be made of existing components, without incurring extra costassociated with new or modified trailer parts.

According to a preferred embodiment of the present invention, the valvedevice for increasing the braking force of the anti-jackknifing brake isdisposed or integrated in an electropneumatic modulator for a parkingbrake—which is implemented by means of at least one spring-actuatedbrake cylinder in the tractor and/or trailer. In this way, ananti-jackknifing brake function can be integrated into an existingparking-brake system with minimal additional complexity and at reducedcost.

According to another embodiment of the present invention, the valvedevice is a separate, independent device. Thus, the anti-jackknifingbrake function can be implemented without relying on a parking-brakemodulator, and, thus, independently of a parking-brake system.

According to a further embodiment of the present invention, the valvedevice for increasing the braking force of the anti-jackknifing brake isinterposed in a trailer reservoir pressure line, which leads from atleast one compressed-air reservoir tank of the tractor to acompressed-air reservoir tank of the trailer, so as to provide acompressed-air reservoir in the trailer. By this arrangement, thetrailer reservoir pressure can be controlled. If the trailer reservoirpressure drops below a preselected value, the spring-actuated brakecylinders are actuated, such that the spring-actuated brake cylindersexert a braking force on the associated wheel brakes. Conversely, if thecompressed-air reservoir in the compressed-air reservoir tank of thetrailer is again raised by means of the valve device, thespring-actuated brake cylinders are repressurized, and, thus, thecorresponding wheel brakes are released, unless the service brake isbeing simultaneously actuated.

According to a still further embodiment of the present invention, thebraking force of the anti-jackknifing brake is generated by means of theservice brake of the trailer. Advantageously, the valve device forincreasing the braking force of the anti-jackknifing brake is then incommunication with a control line, by means of which the brake pressureof the service brake of the trailer is controlled. This control lineruns from a brake pedal of the service brake to at least one brakecylinder of the service brake in the trailer. Thus, by actuation of theelectrical manual operating element, the brake pressure can be raised byinjection of a pressure into the brake-pressure control line for thebrakes of the trailer. In this embodiment, it is also possible to makeuse of existing components in the trailer, and no new or modified partsare necessary in the trailer in order to implement the anti-jackknifingbrake function.

According to another advantageous embodiment of the present invention,the valve device for increasing the braking force of theanti-jackknifing brake can be controlled by a control device. Thiscontrol device has an input for receiving a signal containinginformation about a locked condition of the wheels of the trailer. It isconstructed such that it generates an electrical signal and sends it tothe valve device. By means of the valve device, the braking force of theanti-jackknifing brake can be reduced as a function of the signal. Inthis way, anti-lock protection can be achieved for the anti-jackknifingbrake. If a locking tendency of the wheels of the trailer develops, thebraking force generated by the anti-jackknifing brake is reduced, sothat the wheels tending to lock can turn freely again if necessary, or,because of smaller braking force, can turn at a speed corresponding tothe vehicle's speed. This anti-lock protection can be provided both inthe embodiment of the valve device in combination with the parking brakeand in the embodiment in combination with the service brake.

If anti-lock protection is implemented in conjunction with the parkingbrake, the spring-actuated brake cylinder or cylinders of the traileris/are pressurized, as a function of the electrical signal generated bythe control device, when locking or a locking tendency of a wheel of thetrailer is detected, so that the parking brake is released.Advantageously, the compressed-air reservoir tank of the trailer ispressurized as a function of this signal generated by the controldevice. In this way, the pressure in the spring-actuated brakecylinder(s) is raised and thus the braking force exerted by the parkingbrake is reduced.

According to yet a further embodiment of the present invention, theinformation signal about a potential locked condition of the wheels ofthe trailer is generated by an anti-lock system control unit in thetrailer and transmitted via a suitable interface to the control devicein the tractor. This information signal is either a simple signal, whichglobally displays locking of one or more wheels of the trailer orindicates activation of the anti-lock system of the trailer.Alternatively, this locked-condition information signal is a complexsignal which provides greater information content about the lockingtendency of each individual wheel of the trailer or each individual axleof the trailer.

According to still another embodiment of the present invention, thecontrol device for control of the valve device for increasing thebraking force of the anti-jackknifing brake is integrated into ananti-lock brake system control unit of the tractor. Alternatively, thiscontrol device is integrated in a separate control unit for the parkingbrake. In both cases, use of existing control units can be made so thatno further control units have to be installed for the anti-jackknifingbrake. Thus, additional installation expense can be avoided orminimized.

According to a further embodiment of the present invention, theelectrical signal is a data bus message or the electrical signal can betransformed by the parking-brake modulator or by a control deviceassociated with the parking brake modulator or by another electroniccontrol unit into a data bus message. This data bus message can beevaluated by a brake-control module for control of the brake pressuresfor the brakes or brake cylinders of the tractor and/or trailer, so thatan electrical anti-jackknifing brake control signal can be generated asa function of the evaluated signal and transmitted to the valve deviceconstructed as the trailer control valve in order to influence thebraking force of the anti-jackknifing brake. By means of the operatingelement, therefore, there can be generated, directly or indirectly, adigital data bus message which is evaluated by a brake-control module.After receipt of this message, the brake-control module modulates apressure corresponding to the braking demand by the operator at thetrailer control valve, preferably by sending a predetermined electricalor pneumatic signal to the trailer control valve. Advantageously, a CANbus is used as the data bus, and the data bus message is a CAN data busmessage, for example, as specified by SAE J1939.

The CAN data bus message can be generated either autonomously by theoperating element or a control-element module housing the operatingelement, or by the parking-brake modulator, which receives an analog ordigital electrical signal from the operating element. To this extent, atleast the brake-control module and the operating element or thebrake-control module and the parking-brake modulator are incommunication via the CAN data bus, via which other vehicle componentscan also communicate with one another.

Advantageously, the brake-control module is an “EBS” control module, or,in other words, the control module of an electronic brake system, bywhich the brake pressures at the brakes of the tractor and/or trailercan be electronically controlled. This means that the brake pressures inthe respective wheel brake cylinders can be electronically modulated.Such modulation of the brake pressures can be applied either to eachwheel or to each axle.

According to another embodiment of the present invention, thebrake-control module is the control module of an anti-lock brake system,automatic traction control valves for automatic traction control beingassociated with the brakes, especially the brake cylinders of thebrakes, in such a system.

Preferably, the electrical signal generated by the operating elementrepresents a braking-deceleration value or a brake-pressure value. Thus,a definite braking deceleration can be imposed. That is, the operatorspecifies the negative acceleration with which the vehicle will bebraked. Alternatively, the electrical signal of the operating elementcan be interpreted as the brake-pressure value, so that a brake pressurecorresponding to the position of the operating element is modulated atthe brakes, especially the brake cylinders. In the first case, theacceleration or deceleration of the vehicle is also advantageouslymeasured and fed to a brake-control circuit. In the second case, one ormore brake-pressure sensors are provided to feed the brake-pressurevalues to the brake-control circuit and adjust the desired brakepressure.

Advantageously, the generated data bus message is linked with furthermessages which are generated by a brake power generator, for example,and is respectively weighted and processed in the brake control module.This makes it possible to set priorities for different messages. Linkingtakes place according to a linking mode that determines which messagecontents are most important to defining the braking request. Forexample, a braking request may be generated both by the anti-jackknifingbrake operating element and the service-brake pedal. The linking modethen determines whether the two requests will be added or, for example,whether the higher of the two values will be selected.

Furthermore, by means of the brake-control module, it is possible togenerate status messages, which represent implementation ornon-implementation of the operator's braking demand indicated by meansof the operating element. A status message can be signaled by means of asignal generator, especially of optical or acoustical type, in theoperator's cab. In this way, the vehicle operator receives feedback asto whether his/her braking demand has been successfully implemented inthe anti-jackknifing brake.

The operating element can be advantageously constructed as amulti-position lever, as a slide, especially a slide rheostat, or as arotary knob, especially a rotary rheostat. Preferably, the operatingelement has an integrated electronic module, with which the CAN data busmessage can be generated from the position of the operating element. Inthis way, there is provided an anti-jackknifing brake operating module,with which a variable braking signal can be generated for the trailer,which merely has to be connected to a CAN data bus already present inthe vehicle. The installation complexity for implementation of ananti-jackknifing brake is therefore minimal.

Still other objects and advantages of the present invention will in partbe obvious and will in part be apparent from the specification.

The present invention accordingly comprises the features ofconstruction, combination of elements, and arrangement of parts whichwill be exemplified in the constructions hereinafter set forth, and thescope of the invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the invention, reference is had to thefollowing description taken in connection with the accompanying drawingsin which:

FIG. 1 is a simplified schematic diagram of an air-brake system with ananti-jackknifing brake and an electropneumatic modulator for control ofa parking brake according to one embodiment of the present invention;

FIG. 2 is a more detailed schematic diagram of a portion of theair-brake system depicted in FIG. 1;

FIG. 3 is a schematic diagram of an alternative construction of theembodiment of the air-brake system depicted in FIG. 2;

FIG. 4 is a simplified schematic diagram of an air-brake system with ananti-jackknifing brake and an electropneumatic modulator for control ofa parking brake according to another embodiment of the presentinvention;

FIG. 5 is a more detailed schematic diagram of a portion of theair-brake system depicted in FIG. 4;

FIG. 6 is a schematic diagram of an alternative construction of theembodiment of the air-brake system depicted in FIG. 5;

FIG. 7 is a schematic diagram of a CAN-bus-compatible operating elementfor control of the anti-jackknifing brake function according to afurther embodiment of the present invention;

FIG. 8 is a schematic diagram of an operating element connected to aparking-brake module with an analog output signal for control of theanti-jackknifing brake function according to another embodiment of thepresent invention; and

FIG. 9 is a more detailed view of the construction depicted in FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As used herein, the term “trailer” is to be understood as any mobileunit that can be towed by a tractor; in particular, the term “trailer”includes vehicles resting on a plurality of axles, as well as vehiclesconstructed on only one axle or on one double axle and supported at oneof their ends on the tractor (such vehicles are also known as“semitrailers”).

Referring now to the drawing figures where like reference numerals areused for corresponding parts, FIGS. 1 and 2 depict an air-brake system10 for a vehicle, such as, for example, a commercial vehicle (e.g.,truck or bus), that can be operated with a trailer. In FIG. 1, twowheels 12 of a front axle and two wheels 14 of a rear axle are shown.Wheels 12 of the front axle are braked via brake cylinders 16, andwheels 14 of the rear axle are braked via brake cylinders 18.

It should be understood that, even if only four wheels on two axles arerepresented, the present invention is not limited to such a number ofwheels or number of axles. Indeed, the present invention also hasapplication with respect to vehicles with more than four wheels or morethan two axles.

Brake cylinders 18 of the rear axle are constructed as combinationspring-actuated/diaphragm cylinders. In FIG. 2, only one such brakecylinder 18 is shown, for reasons of simplified illustration; it shouldbe understood that a plurality of such brake cylinders 18 is present.These spring-actuated/diaphragm cylinders are provided with a diaphragmpart 20 as well as a spring-actuated part 22. Diaphragm part 20 is usedto provide a service brake, which is actuated pneumatically via a brakepedal 24. Spring-actuated part 22 is used to provide a locking brake(also known as a parking brake). This spring-actuated part 22 isprovided with an actuator spring 26, which engages the wheel brake ofthe corresponding wheel when spring-actuated part 22 is vented. Thevehicle is then braked or immobilized. By admission of compressed air,this spring-actuated part 22 can compress actuator spring 26 and thusrelease the parking brake. Spring-actuated part 22 can be constructedlargely independently of (and, in principle, separately from) diaphragmpart 20 of the service brake. Nevertheless, combinationspring-actuated/diaphragm cylinders, in which both the service brake andthe parking brake are implemented, are preferred. Accordingly,hereinafter, the term “spring-actuated brake cylinder” should beunderstood to include such combination spring-actuated/diaphragmcylinders.

Wheels 12, 14 are equipped with wheel-speed sensors 28, 30. Sensors 28,30 are connected via electrical lines 32, 34 to a control unit 36.

Wheel-speed sensors 28, 30, respectively, measure the speed ofassociated wheels 12, 14 in order to detect whether the respective wheel12, 14 is locked or tending to lock. Control unit 36 evaluates themeasured wheel speeds and, if necessary, reduces the brake pressureacting on brake cylinders 16, 18 by means of valve devices 38, 40.

A compressed-air supply device 42 supplies two compressed-air reservoirtanks 44, 46 with compressed air. The first compressed-air reservoirtank 44 is used to provide compressed air for the brakes of the rearaxle. The second compressed-air reservoir tank 46 is used to providecompressed air for the brakes of the front axle. The pressure ofcompressed-air reservoir tank 46 for the brakes of the front axle isrouted to an airflow-boosting valve device constructed as a relay valve48. This relay valve 48 also has a control input 50 which is suppliedwith a modulated pressure 52 for brake cylinder 16 of the front axle.Pressure 52 is made available by brake-actuating device 54 incommunication with brake pedal 24.

Relay valve 48 has a dual output 56, which is in communication withvalve devices 38 of each brake cylinder 16 of the front axle. Valvedevices 38 as well as valve devices 40 of the rear axle are connectedvia electrical lines 58, 60 to control unit 36.

Via compressed-air lines, pressure reservoir tank 44 is in communicationwith a further airflow-boosting valve device constructed as relay valve62. This relay valve has a control input 64, to which a modulatedpressure 66 for brake cylinders 18 of the rear axle is admitted viacompressed-air lines. This pressure 66 is provided by brake-actuatingdevice 54.

Relay valve 62 also has a dual output 68, which is in communication withvalve devices 40 for brake cylinders 18 of the rear axle.

By actuation of brake pedal 24, a modulated pressure 52 or 66 isprovided for the front axle or rear axle, respectively. The airflowprovided at the respective pressure is boosted by means of relay valves48 and 62, respectively. After airflow boosting, the correspondingpressure is then relayed via valve devices 38, 40 to brake cylinders 16,18, unless these valve devices 38, 40 reduce this pressure, for examplebecause control unit 36 has detected locking or a locking tendency ofone or more wheels. In this way, control unit 36 in combination withwheel-speed sensors 28, 30 provides an anti-lock system.

Modulated pressures 52, 66 for the front axle and rear axle,respectively, are further fed to a select-high valve 70, which selectsthe higher of the two modulated pressures 52, 66 and provides it at itsoutput 72. This pressure is fed as a service-brake pressure via acontrol line 74 to a compressed-air coupling 76, at which there can beconnected a corresponding compressed-air line of a trailer coupled tothe tractor.

Via a further compressed-air coupling 78, compressed air for acompressed-air reservoir tank in the trailer is also made available. Viaa compressed-air line, this compressed-air coupling 78 is incommunication with an electropneumatic modulator 80 for the parkingbrake of the tractor or also of the trailer.

Modulator 80 has a double check valve 82, via which modulator 80 is incommunication with compressed-air reservoir tanks 44, 46. Modulator 80is therefore supplied with the higher of the two reservoir pressures ofcompressed-air reservoir tanks 44, 46. Simultaneously, this double checkvalve 82 ensures that the pressure in modulator 80 will not dropsuddenly in the event of a pressure drop in one or both compressed-airreservoir tanks 44, 46.

As a function of a signal fed via electrical lines 84 from control unit36, modulator 80 generates, at modulator output 86, a modulated pressurethat is fed via an interposed overload-protection valve or select-highvalve 88 to each spring-actuated part 22 of combinationspring-actuated/diaphragm cylinder 18 of the rear axle. Thisoverload-protection valve 88 is connected between spring-actuated part22, output 86 and brake-actuating device 54. Overload-protection valve88 selects the higher of the two pressures present at its inputs leadingto brake-actuating device 54 or to output 86 of modulator 80 and passesit via its output to spring-actuated part 22 of brake cylinder 18.Overload-protection valve 88 prevents addition of the braking forceexerted by the service brake and the braking force exerted by theparking brake or actuator spring 26, in this way preventing mechanicaloverloading of the brake mechanism in the wheel brake associated withbrake cylinder 18.

For simplicity, diaphragm part 20 is shown directly connected tobrake-actuating device 54 in FIG. 2. Also for reasons of simplicity,relay valve 62 (see FIG. 1) is not shown in FIG. 2.

It should be understood that relay valves 48 and 62 are optional. Ifbrake-actuating device 54 makes modulated pressures available with anadequate airflow, there is no need to employ these relay valves.

The structure of modulator 80 will now be explained in greater detail onthe basis of FIG. 2. Modulator 80 is provided with a first valve device90, which is an electrically actuatable solenoid valve. This valvedevice 90 has three ports. A first port 92 is in communication withdouble check valve 82 (depicted as integrated in the modulator) and,thus, with the higher of the two reservoir pressures of compressed-airreservoir tanks 44, 46. Valve device 90 also has a second port 94 whichis used for venting. Additionally, valve device 90 has a third port 96which is in communication with control input 98 of a relay valve 100serving as an airflow-boosting valve device. This relay valve has threefurther ports: one inlet 102 of relay valve 100 is also incommunication, via double check valve 82, with the higher of the tworeservoir pressures of compressed-air reservoir tanks 44, 46. One outlet104 of relay valve 100 is in communication with output 86 of modulator80.

At its outlet 104, relay valve 100 delivers a pressure present at itscontrol input 98, but with a higher airflow, to the extent that such isrequired. Via a venting outlet 106, relay valve 100 can react rapidly todissipate the pressure at outlet 104 if the control pressure at controlinput 98 drops.

Via control unit 36, the pressure at output 86 of modulator 80 can becontrolled by means of valve device 90 and relay valve 100. In this way,the pressure in spring-actuated part 22 of combinationspring-actuated/diaphragm cylinder 18 can also be controlled. If thepressure in spring-actuated part 22 is high, actuator spring 26 iscompressed and the parking brake is released. In contrast, if thepressure in spring actuator part 22 is low, meaning that spring-actuatedpart 22 is vented, the actuator spring expands and the parking brake isengaged.

Valve device 90 has a plurality of states. When it is de-energized, itoccupies a first state, in which throttled venting of spring-actuatedpart 22 takes place.

Valve device 90 occupies a second, energized state in which the pressureis held at control input 98 and therefore in spring-actuated part 22,since control input 98 in this second state is isolated from first port92 of valve device 90.

Valve device 90 occupies a third, energized state in which first port 92is in communication with third port 96, meaning that the higher of thetwo reservoir pressures is being passed through to control input 98 ofrelay valve 100. Thus, the pressure in spring-actuated part 22 alsorises, in turn compressing the actuator spring and thus releasing theparking brake.

In a fourth state, which is also energized, sudden venting of controlinput 98 via the second port of valve device 90 occurs. Thus, thepressure at outlet 104 of relay valve 90 also drops suddenly. This inturn leads to a rapid drop of the pressure in spring-actuated part 22and, thus, to rapid engagement of the parking brake.

In this way, there is provided a parking brake that can be electricallycontrolled by means of control unit 36.

Modulator 80 is also provided with a further valve device 108 which isstructured just as valve device 90 with a plurality of states and aplurality of ports. A first port 110 of valve device 108 is incommunication with the higher of the two reservoir pressures ofcompressed-air reservoir tanks 44, 46. A second port 112 of valve device108 forms a vent. A third port 114 of valve device 108 is incommunication with compressed-air coupling 78.

Valve device 108 is also connected electrically to control unit 36.Preferably, it is constructed to be the same as valve device 90, inwhich case the foregoing description of the different states isapplicable by reference. However, since port 114 of valve device 108 isin communication with coupling 78 for the reservoir pressure in thetrailer, the reservoir pressure in the trailer can be raised, lowered ormaintained by means of valve device 108. Since the reservoir pressure inthe trailer also influences the parking brake of the trailer, theparking brake of the trailer can be actuated, or in other words engagedor released, via control of the reservoir pressure in the trailer. Thus,if the reservoir pressure in the trailer drops below a preselected limitvalue, the spring actuators of the combination spring-actuated/diaphragmcylinders that are also provided in the trailer are activated and theparking brake of the trailer is engaged. However, if the reservoirpressure has exceeded a certain threshold value, the parking brake isreleased. Braking of the trailer can then take place by means of theservice brake.

Valve device 108 and, thus, the reservoir pressure in the trailer iscontrolled via control unit 36. Control unit 36 is also connected viaelectrical lines to a manual operating element 116. This operatingelement is constructed as an analog or digital signal generator, forexample. Depending on the electrical signal generated by operatingelement 116, control unit 36 generates an electrical control signal forvalve device 108, in this way, controlling the pressure in thecompressed-air reservoir tank of the trailer.

Control unit 36 is also connected to two further electrical operatingelements 118, 120 which, in common with operating element 116, aredisposed in the operator's cab. Operating elements 118 and 120 are usedfor actuation of the parking brake of the tractor or of the trailer. Theparking brake of the tractor or the parking brake of the trailer isactuated, or, in other words, engaged or released, by actuation ofoperating element 118 or by actuation of operating element 120,respectively.

Valve device 90 and/or valve device 108 can be constructed as 3/4-waysolenoid valves, as illustrated in FIG. 2, in which case they aresolenoid valves with three pneumatic ports and four states.Alternatively, however, they can also be constructed as double-armaturesolenoid valves. As a further alternative, the corresponding valvedevice 90 or 108 can be constructed as a combination of one 3/2-waysolenoid valve and one 2/2-way solenoid valve constructed as a holdingvalve.

As an example, FIG. 3 shows a construction of valve device 108′ as a3/2-way solenoid valve 122 as well as a 2/2-way solenoid valve 124. Inother respects, FIG. 3 corresponds to the embodiment depicted in FIG. 2,although valve device 108 shown therein is disposed outside modulator80′, so that only the parking-brake function of the tractor, and not theparking and anti-jackknifing brake function of the trailer, isimplemented in modulator 80′. Indeed, it is advantageous to includevalve device 108′ also in the modulator; however, this is not necessary.Alternatively, therefore, valve device 108′ can be provided separately.Also, in this separate arrangement, valve device 108′ can be configuredas a 3/4-way solenoid valve, as a double-armature solenoid valve or as acombination of a 3/2-way solenoid valve with a 2/2-way solenoid valve.

As depicted in FIGS. 2 and 3, diverse pressures can be measured by meansof pressure sensors 126, 128, 130, 132 and 134. Pressure sensor 126measures the pressure in compressed-air reservoir tank 44. The pressurein compressed-air reservoir tank 46 is measured by means of pressuresensor 128. Pressure sensor 130 measures the pressure at output 86 ofmodulator 80, 80′ or at outlet 104 of relay valve 100. Pressure sensor132 measures the pressure at the third port of valve device 108, 108′ orat compressed-air coupling 78, and, thus, it measures the reservoirpressure of a coupled trailer. The control pressure of the service brakefor the trailer is measured by means of pressure sensor 134. Allmeasured pressures are evaluated in control unit 36 in order thatparticular conditions can be recognized if necessary and thatcommensurate measures for control of the solenoid valves can beinitiated if necessary.

Indeed, measurements of all cited pressures are advantageous. However,it is not necessary to measure all cited pressures in every embodimentof the present invention. One or more of the cited pressure measurementsmay be omitted in alternative embodiments. In particular, pressuresensor 134 and, thus, measurement of the control pressure of the servicebrake of the trailer can be omitted in the embodiments of the presentinvention depicted in FIGS. 2 and 3. Furthermore, depending onembodiment, all or only some of the cited pressure sensors may bedisposed inside or outside the modulator.

FIGS. 4 and 5 show a further embodiment of the present invention thatbroadly corresponds to the embodiment shown in FIGS. 1 and 2. To thisextent, the foregoing discussion is applicable by reference, unlessotherwise indicated hereinafter. In particular, like reference symbolsdenote like parts.

A substantial difference with respect to the embodiment shown in FIGS. 4and 5 lies in the configuration of electropneumatic modulator 80″ forthe parking brake. As shown in FIG. 5, this now encompasses select-highvalve 70 as well as pressure sensor 134, among other components.

Both modulated pressure 52 for the front axle and modulated pressure 66for the rear axle are fed to modulator 80″. Furthermore, modulator 80″has a pneumatic connection to compressed-air coupling 76 for the controlpressure of the service brake of the trailer.

In contrast to the embodiments depicted in FIGS. 1, 2 and 3, in whichthe spring-actuated parts of the combination spring-actuated/diaphragmcylinders of the trailer are used to implement the anti-jackknifingbrake function, in the embodiment depicted in FIGS. 4 and 5 and also inFIG. 6, the service brake is used to implement the anti-jackknifingbrake function. The advantage of using the service brake lies in thefact that automatic anti-lock protection already exists by virtue of theanti-lock system that is usually already present in the trailer, plusthe fact that higher braking forces can be transmitted by the servicebrake. Furthermore, the response times of the service brake aresometimes much shorter than when the spring-actuated parts of thecombination spring-actuated/diaphragm cylinders are used.

By analogy to the embodiment of the present invention depicted in FIG.2, the embodiment depicted in FIGS. 4 and 5 also uses valve device 108,which is already available, in order to pressurize or vent viacompressed-air coupling 78 as well as an associated reservoir line, inorder to pressurize or vent the compressed-air reservoir tank in thetrailer and, via the pressure in this compressed-air reservoir tank,indirectly the spring-actuated parts of the combinationspring-actuated/brake cylinders of the trailer. However, changeovervalve 136 is additionally connected downstream from valve device 108.Upon actuation of the anti-jackknifing brake by means of operatingelement 116, changeover valve 136 is energized and thus actuated. Inthis way, the spring actuators of the trailer remain pressurized, sincechangeover valve 136 conveys the higher of the two reservoir pressuresof compressed-air reservoir tanks 44, 46 directly through tocompressed-air coupling 78 for the reservoir pressure of the trailer.The braking force exerted by the respective spring-actuated part of thecombination spring-actuated/brake cylinders of the trailer is therebyminimized or reduced to zero.

At the same time, control line 74, which is in communication withcompressed-air coupling 76 for the control pressure, is placed incommunication with valve device 108, so that the pressure in the servicebrake of the trailer can be modulated. In this way, the service brakepressure in the trailer can be changed electropneumatically via controlunit 36 and manual operating element 116.

As an example, changeover valve 136 is constructed as a 4/2-way solenoidvalve with four pneumatic ports and two states. In a first, de-energizedstate, the trailer reservoir pressure line can be controlled by means ofvalve device 108 with respect to the pressure conveyed to coupling 78for the reservoir pressure in the trailer, while control line 74 forcontrol of the brake pressure of the service brake for the trailercannot be influenced by modulator 80″. In a second, energized state ofchangeover valve 136, however, the trailer reservoir pressure line ispneumatically in communication with the reservoir pressure of thetractor, and control line 74 for control of the service brake pressurein the trailer is pressurized with compressed air or vented as necessaryby means of valve device 108.

The trailer can also be braked with foot brake pedal 24. For thispurpose, there is interposed in control line 74 a select-high valve 138,which is in communication with changeover valve 136. This select-highvalve 138 relays the higher of the two pressures present at its inputsto compressed-air coupling 76 for the control pressure of the servicebrake of the trailer. The higher of the two modulated pressures 52, 66is present at its first input, and the modulated pressure of the thirdport 114 of valve device 108 is present at its second input, whenchangeover valve 136 is energized.

The pressure in control line 74 can be adjusted by means of pressuresensor 134. Alternatively, the pressure in control line 74 is adjustedon the basis of the measured braking deceleration, taking intoconsideration the position of operating element 116 and, if applicable,the actuation of brake pedal 24. In this alternative scheme, pressuresensor 134 can be omitted.

As explained above in connection with FIG. 2, valve device 108 can beconstructed as a 3/4-way solenoid valve with four states. In this way,the pressure in the control line not only can be raised and lowered butalso held. In an alternative embodiment, a simpler 3/2-way solenoidvalve can be used instead of this valve, although it has nopressure-holding position but only two positions for raising or loweringthe pressure. Pressure holding can be achieved by operating this valvein pulsed mode.

In addition to a 3/2-way solenoid valve, however, there can also beprovided a holding valve, for example in the form of a 2/2-way solenoidvalve, so that the pressure in control line 74 can also be held. Pulsedoperation of the 3/2 solenoid valve is then obviated, thus avoidingunnecessary air consumption.

FIG. 6 depicts a further embodiment of the present invention. Incontrast to the embodiment depicted in FIG. 2 or FIG. 3, according tothe embodiment of FIG. 6 the anti-jackknifing brake function can be usedboth via the spring-actuated part of the combinationspring-actuated/brake cylinders of the trailer and via the service brakeof the trailer. To this extent, valve 108 is provided in order to raise,lower or hold the reservoir pressure in the trailer.

The pressure in control line 74 can also be raised via a further valvedevice 140 in order to actuate the service brake in the trailer.Similarly, as in the embodiment depicted in FIG. 4, a select-high valve138 is interposed in control line 74 for this purpose. Once again, oneinput of this select-high valve 138 is in communication with select-highvalve 70 for selection of the higher of the two modulated pressures 52,66. The second input of select-high valve 138 is in communication withvalve device 140, which, in turn, is in communication with the higher ofthe two reservoir pressures of compressed-air reservoir tanks 44, 46. Bymeans of valve device 140, the pressure in control line 74 can be raisedin order to actuate the service brake of the trailer. Valve device 140is actuated via control unit 36, which, in turn, can be controlled byoperating element 116.

Preferably, valve device 140 is constructed as a combination of a3/2-way solenoid valve 142 and a 2/2-way solenoid valve or holding valve144. Also, valve device 140 is preferably disposed outside modulator80′″, or, in other words separately. However, it can also be integratedin modulator 80′″.

FIGS. 7 and 8 show operating elements for control of theanti-jackknifing brake function in brake systems linked by a CAN databus.

FIG. 7 shows operating element 116′, which, via a CAN data bus 146, cansend a digital signal to an EBS control unit 148 to control anelectronic brake system. The CAN data bus message of operating element116′ represents one position of operating element 116′, which, in turn,represents a braking demand of the vehicle operator for theanti-jackknifing brake. EBS control module 148 sends electrical signalsnot only to the electropneumatic axle modulators of front axle 150 andof rear axle 152 of the tractor for control of the respective brakepressures at these axles, but also to a trailer control valve 154.Trailer control valve 154 is therefore connected to the EBS controlmodule via electrical lines 156. Trailer control valve 154 outputs amodulated pressure for the brakes of the trailer at a compressed-airport of a brake control line. In this way, actuation of operatingelement 116′ can be controlled or adjusted to a modulated pressure inthe brake control line from the trailer control valve to the trailerbrakes.

In the embodiment of the present invention depicted in FIG. 7, operatingelement 116′ already has an electronic module with which it can generatea CAN data bus signal from a position of the operating element. Indeed,such an electronic module directly on operating element 116′ isadvantageous. However, it should be understood that the CAN data bussignal can also be generated at other locations.

FIG. 8 depicts an alternative embodiment of the present invention inwhich the CAN data bus signal is generated at another location, forexample by a parking-brake modulator 158. In this practical example,operating element 116″ generates an analog signal which is conducted viaelectrical lines 160 to parking-brake modulator 158. In this embodiment,parking-brake modulator 158 has an electronic module in order togenerate a CAN data bus signal from the analog signals obtained fromoperating element 116″ via electrical lines 160. Once again, this CANdata bus signal represents a position of operating element 116″ and,therefore, a braking demand of the vehicle operator. The CAN data bussignal is sent from parking-brake modulator 158 via a CAN bus 162 to EBScontrol module 148, which in turn, just as EBS control module 148 shownin FIG. 7, provides electrical signals for the brake pressures at frontaxle 150 and rear axle 152 as well as via electrical lines 156 totrailer control valve 154.

According to a further embodiment of the present invention, theoperating element generates not an analog signal but instead a digitalsignal, although not a signal that is compatible with the CAN data bus.This digital signal is, in turn, provided to parking-brake modulator158, which generates a CAN data bus signal from the digital signal.Otherwise, this embodiment operates in the same way as the embodimentdepicted in FIG. 8.

FIGS. 7 and 8 differ only in regard to the provision of the data bussignal, which, in the embodiment shown in FIG. 7, is generated directlyby operating element 116′, whereas, in the embodiment shown in FIG. 8,it is generated only indirectly by operating element 116″, namely byinterposed parking-brake modulator 158 or by another electronic controlunit, such as, for example, a vehicle guidance computer.

FIG. 9 is a more detailed view of the embodiment of the presentinvention depicted in FIG. 7. In this case, operating element 116′ isconstructed as an operating lever. On operating element 116′ there isprovided a displacement/voltage converter 164 which converts a positionof the operating lever or a value traveled by the operating lever intoan electrical voltage. This displacement/voltage converter 164 isconnected to an electronic module 166 which converts the electricalsignal output by the displacement/voltage converter into a CAN busmessage. Among other features, this bus message has a digital valueequal to 8 or 16 bits in length. Thus, 2⁸ or 2¹⁶ different positions ofoperating element 116′ can be coded and a variable brake signal can begenerated.

CAN bus module 166 is advantageously integrated in operating element116′. However—as in the embodiment depicted in FIG. 8—it can also bedisposed separately in another unit, especially, an electronic controlunit.

CAN bus module 166 is connected via CAN data bus 146 to EBS controlmodule 148.

EBS control module 148 is also connected to wheel sensors 170 mounted inthe region of wheels 168 of front axle 150 as well as to wheel sensors174 mounted in the region of wheels 172 of rear axle 152. Furthermore,EBS control module 148 is connected to rear-axle brake modulator 176and, via this rear-axle brake modulator 176, to trailer control valve154. Also, EBS control module 148 is connected to a brake powergenerator of brake-actuating device 54 and to ABS valves 178. EBScontrol module 148 is further connected to a relay valve 180 for controlof the brake pressures at front axle 150, and to an electricalconnecting device, such as a plug 182, functioning as an interface, bymeans of which the control unit can exchange electrical signals,especially data, with the trailer.

All cited connections of EBS control module 148 are electricalconnections established by means of electrical lines.

In normal operation, actuation of brake-actuating device 54 causes thebrake power generator associated therewith to send an electrical signalto EBS control module 148. EBS control module 148, taking other vehicleconditions into consideration, such as, for example, the values of wheelsensors 170, 174, calculates electrical signals for relay valve 180 andrear-axle brake modulator 176, so that relay valve 180 and rear axlebrake modulator 176 can modulate appropriate brake pressures as afunction of the electrical signals fed to them.

This electronic brake system also takes over the function of ananti-lock system. If one or more of wheel sensors 170, 174 signals awheel speed, especially a lower speed, that does not correspond to thevehicle speed, the brake pressure can be reduced by means of ABS valves178 and corresponding valves (not shown in FIG. 9) so that wheels thatmay be locked or exhibiting a tendency to lock are acted on with a lowerbrake pressure and, thus, can regain the speed of revolutioncorresponding to the vehicle speed.

The electrical signal generated by operating element 116′ passes firstvia CAN data bus 146 to EBS control module 148 and is then conducted asan electrical control signal via rear-axle brake modulator 176 totrailer control valve 154 and, from there, via a compressed-air port 188to the brake control line leading to the trailer brakes. Besides thiscompressed-air port 188 for the brake control line, trailer controlvalve 154 is in communication with a further compressed-air port,namely, compressed-air supply port 190 for the trailer.

The described signal path from operating element 116′ to thecompressed-air port of brake-control line 188 is illustrated by hatchingin FIG. 9.

Although operating element 116′ is illustrated as an anti-jackknifingbrake lever module in FIG. 9, other electrical signal generators can beused in alternative embodiments of the present invention. It should beunderstood that the present invention is not limited to a lever-typesignal generator. Slide regulators or rotary regulators ormomentary-contact switches with a display can also be used.

On the whole, the present invention makes it possible to achieve ananti-jackknifing brake function electropneumatically without having toroute compressed-air lines in the operator's cab for the purpose. Thisanti-jackknifing brake function can be implemented in the modulator forthe parking brake, in which case either the spring-actuated parts of thecombination spring-actuated/brake cylinders in the trailer or theservice brake of the trailer are/is used for this purpose. However, theanti-jackknifing brake function can also be implemented by means ofspecial valve devices, such as 3/2-way solenoid valves and holdingvalves, so that it is independent of the parking-brake modulator. Forthis purpose, pressure control in the trailer reservoir pressure lineand/or pressure control in the control line for the brake pressure inthe trailer can also be used to implement an anti-jackknifing brakefunction.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained, andsince certain changes may be made in the above constructions withoutdeparting from the spirit and scope of the invention, it is intendedthat all matter contained in the above description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed and all statements of the scope of the invention which, as amatter of language, might be said to fall therebetween.

1. An electrically controlled brake system for a tractor vehicle, saidtractor vehicle being connectable to a trailer vehicle, said brakesystem comprising an anti-jackknifing brake which acts on only brakes ofsaid trailer vehicle, said anti-jackknifing brake being actuatable by amanually operable electrical operating element, said electricaloperating element being constructed and arranged to generate anelectrical operating element signal to control a valve device forinfluencing braking force of said anti-jackknifing brake.
 2. The brakesystem according to claim 1, wherein said electrical operating elementsignal is an analog signal which is variable at least one of infinitelyand in multiple stages.
 3. The brake system according to claim 1,wherein said electrical operating element signal is a digital signal bywhich a plurality of different values are representable.
 4. The brakesystem according to claim 1, wherein said valve device for influencingbraking force of said anti-jackknifing brake is an independent valvedevice.
 5. The brake system according to claim 1, wherein said valvedevice for influencing braking force of said anti-jackknifing brake isat least one of disposed in and integrated in an electropneumaticmodulator for a parking brake implemented by means of at least onespring-actuated brake cylinder in at least one of said tractor vehicleand said trailer vehicle.
 6. The brake system according to claim 5,wherein said braking force of said anti-jackknifing brake is generatedby means of said at least one spring-actuated brake cylinder of saidtrailer vehicle.
 7. The brake system according to claim 6, wherein saidvalve device for influencing braking force of said anti-jackknifingbrake is interposed in a trailer reservoir pressure line from at leastone compressed-air reservoir tank of said tractor vehicle to acompressed-air reservoir tank of said trailer vehicle to provide acompressed-air reservoir in said trailer vehicle and to control trailerreservoir pressure.
 8. The brake system according to claim 1, whereinsaid braking force of said anti-jackknifing brake is generated by meansof a service brake of said trailer vehicle.
 9. The brake systemaccording to claim 8, wherein said valve device for influencing brakingforce of said anti-jackknifing brake is in pneumatic communication witha control line from a brake-actuating device of said service brake to atleast one brake cylinder of said service brake to raise brake pressureof said service brake in said control line upon actuation of saidelectrical operating element.
 10. The brake system according to claim 1,wherein said valve device for influencing braking force of saidanti-jackknifing brake occupies a first state when it is de-energized inwhich said at least one spring-actuated brake cylinder of said trailervehicle is vented.
 11. The brake system according to claim 10, whereinsaid valve device for influencing braking force of said anti-jackknifingbrake occupies a second state when it is energized in which a trailerreservoir pressure line from at least one compressed-air reservoir tankof said tractor vehicle to a compressed-air reservoir tank of saidtrailer vehicle is shut off to isolate said at least one compressed-airreservoir tank of said tractor vehicle pneumatically from saidcompressed-air reservoir tank of said trailer vehicle.
 12. The brakesystem according to claim 11, wherein said valve device for influencingbraking force of said anti-jackknifing brake occupies a third state whenit is further energized in which said trailer reservoir pressure line isopen to place said at least one compressed-air reservoir tank of saidtractor vehicle in pneumatic communication with said compressed-airreservoir tank of said trailer vehicle.
 13. The brake system accordingto claim 12, wherein said valve device for influencing braking force ofsaid anti-jackknifing brake occupies a fourth state when it is furtherenergized in which at least one spring-actuated brake cylinder of saidtrailer vehicle is vented in throttled manner.
 14. The brake systemaccording to claim 1, wherein said valve device for influencing brakingforce of said anti-jackknifing brake is a 3/4-way solenoid valve. 15.The brake system according to claim 1, wherein said valve device forinfluencing braking force of said anti-jackknifing brake is adouble-armature solenoid valve.
 16. The brake system according to claim1, wherein said valve device for influencing braking force of saidanti-jackknifing brake includes both a 3/2-way solenoid valve and a2/2-way solenoid valve.
 17. The brake system according to claim 1,wherein said valve device for influencing braking force of saidanti-jackknifing brake includes a 4/2-way solenoid valve having fourpneumatic ports and two states, and wherein, in a first, de-energizedone of said two states, a trailer reservoir pressure line from at leastone compressed-air reservoir tank of said tractor vehicle to acompressed-air reservoir tank of said trailer vehicle is controlled bymeans of a further valve with respect to pressure, and a control linefrom a brake-actuating device of a service brake of said trailer vehicleto at least one brake cylinder of said service brake for control ofservice brake pressure is not influenced, and wherein, in a second,energized one of said two states, said trailer reservoir pressure lineis in pneumatic communication with said at least one compressed-airreservoir tank of said tractor vehicle, and said control line ispressurized with compressed air from said at least one compressed-airreservoir tank of said tractor vehicle by means of said further valve.18. The brake system according to claim 1, wherein said valve device forinfluencing braking force of said anti-jackknifing device iscontrollable by a control device having an input for receiving a signalcontaining information as to a locked condition of wheels of saidtrailer vehicle, said control device being constructed and arranged togenerate an electrical control device signal to said valve device toeffect a reduction in said braking force of said anti-jackknifing brakeby said valve device as a function of said electrical control devicesignal.
 19. The brake system according to claim 18, further comprisingat least one spring-actuated brake cylinder of said trailer vehicle,said at least one spring-actuated brake cylinder of said trailer vehiclebeing pressurized as a function of said electrical control devicesignal.
 20. The brake system according to claim 19, further comprising acompressed-air reservoir tank of said trailer vehicle, saidcompressed-air reservoir tank of said trailer vehicle being pressurizedas a function of said electrical control device signal.
 21. The brakesystem according to claim 18, wherein said signal containing informationas to a locked condition of wheels of said trailer vehicle is generatedby an anti-lock system control unit of said trailer vehicle and istransmitted to said control device.
 22. The brake system according toclaim 18, wherein said control device is integrated in an anti-locksystem control unit of said tractor vehicle.
 23. The brake systemaccording to claim 18, wherein said control device is integrated in aparking brake control unit.
 24. The brake system according to claim 1,wherein said valve device is a trailer control valve, and wherein saidelectrical operating element signal is at least one of (a) a data busmessage and (b) transformable into a data bus message by at least one of(i) a parking brake modulator and (ii) a control device associated withsaid parking brake modulator and (iii) an electronic control unit, saidbrake system further comprising a brake-control module for controllingbrake pressure in brakes of at least one of said tractor vehicle andsaid trailer vehicle, said brake-control module being constructed andarranged to evaluate said data bus message, generate an electricalanti-jackknifing brake control signal as a function of said data busmessage and transmit said data bus message to said trailer control valveto influence braking force of said anti-jackknifing brake.
 25. The brakesystem according to claim 24, wherein said data bus message is a CANdata bus message transmitted via a CAN data bus.
 26. The brake systemaccording to claim 25, wherein said CAN data bus connects saidelectrical operating element and said brake-control module.
 27. Thebrake system according to claim 25, wherein said CAN data bus connectssaid parking brake modulator and said brake-control module.
 28. Thebrake system according to claim 25, wherein said electrical operatingelement includes an electronic module for generating said CAN data busmessage.
 29. The brake system according to claim 24, wherein saidbrake-control module is an electronic brake system control module forelectronically controlling brake pressures at said brakes.
 30. The brakesystem according to claim 24, wherein said brake-control module is acontrol module of an anti-lock brake system including automatic tractioncontrol valves associated with said brakes.
 31. The brake systemaccording to claim 24, wherein said electrical operating element signalrepresents at least one of a braking-deceleration value and abrake-pressure value.
 32. The brake system according to claim 24,wherein said data bus message is linked in said brake-control modulewith further messages processed in weighted form.
 33. The brake systemaccording to claim 24, wherein said brake-control module is adapted togenerate a status message representing at least one of implementationand non-implementation of braking demand by an operator of said tractorvehicle as indicated by means of said electrical operating element, saidstatus message being signaled to said operator by means of a signalgenerator in a cab of said tractor vehicle.
 34. The brake systemaccording to claim 33, wherein said signal generator is at least one ofan optical and acoustical type.
 35. The brake system according claim 1,wherein said electrical operating element is a multi-position lever. 36.The brake system according to claim 1, wherein said electrical operatingelement is a slide.
 37. The brake system according to claim 36, whereinsaid electrical operating element is a slide rheostat.
 38. The brakesystem according to claim 1, wherein said electrical operating elementis a rotary knob.
 39. The brake system according to claim 38, whereinsaid electrical operating element is a rotary rheostat.